The present invention relates generally to in silico design of organisms, and more specifically to organisms having 1,4-butanediol biosynthetic capability.
1,4-Butanediol (BDO) is a four carbon dialcohol that currently is manufactured exclusively through various petrochemical routes. BDO is part of a large volume family of solvents and polymer intermediates that includes gamma-butyrolactone (GBL), tetrahydrofuran (THF), pyrrolidone, N-methylpyrrolidone (NMP), and N-vinyl-pyrrolidone. The overall market opportunity for this family exceeds $4.0 B.
Approximately 2.5B lb BDO is produced globally per year with 4-5% annual growth and a recent selling price ranging from $1.00-1.20/lb. The demand for BDO stems largely from its use as an intermediate for polybutylene terephthalate (PBT) plastic resins, polyurethane thermoplastics and co-polyester ethers. BDO also serves as a primary precursor to THF, which is employed as an intermediate for poly(tetramethylene glycol) PTMEG copolymers required for lycra and spandex production. Approximately 0.7 B lb of THF is produced globally per year with an annual growth rate over 6%. A significant percentage of growth (>30%) for both BDO and THF is occurring in Asia (China and India). GBL currently is a smaller volume (0.4 B lb/year) product which has numerous applications as a solvent, as an additive for inks, paints, and dyes, as well as the primary precursor to pyrrolidone derivatives such as NMP.
Conventional processes for the synthesis of BDO use petrochemical feedstocks for their starting materials. For example, acetylene is reacted with 2 molecules of formaldehyde in the Reppe synthesis reaction (Kroschwitz and Grant, Encyclopedia of Chem. Tech., John Wiley and Sons, Inc., New York (1999)), followed by catalytic hydrogenation to form 1,4-butanediol. It has been estimated that 90% of the acetylene produced in the U.S. is consumed for butanediol production. Alternatively, it can be formed by esterification and catalytic hydrogenation of maleic anhydride, which is derived from butane. Downstream, butanediol can be further transformed; for example, by oxidation to γ-butyrolactone, which can be further converted to pyrrolidone and N-methyl-pyrrolidone, or hydrogenolysis to tetrahydrofuran (FIG. 1). These compounds have varied uses as polymer intermediates, solvents, and additives, and have a combined market of nearly 2 billion lb/year.
The conventional hydrocarbon feedstock-based approach utilizes methane to produce formaldehyde. Thus, a large percentage of the commercial production of BDO relies on methane as a starting material. The production of acetylene also relies on petroleum-based starting material (see FIG. 1). Therefore, the costs of BDO production fluctuate with the price of petroleum and natural gas.
It is desirable to develop a method for production of these chemicals by alternative means that not only substitute renewable for petroleum-based feedstocks, and also use less energy- and capital-intensive processes. The Department of Energy has proposed 1,4-diacids, and particularly succinic acid, as key biologically-produced intermediates for the manufacture of the butanediol family of products (DOE Report, “Top Value-Added Chemicals from Biomass”, 2004). However, succinic acid is costly to isolate and purify and requires high temperatures and pressures for catalytic reduction to butanediol.
Thus, there exists a need for alternative means for effectively producing commercial quantities of 1,4-butanediol and its chemical precursors. The present invention satisfies this need and provides related advantages as well.